The purpose of this investigation is to examine various aspects of adrenocortical function in sick and well premature infants and in infants with intrauterine growth retardation. In particular, adrenal cortical and feto-placental unit function will be evaluated in prematures with respiratory distress syndrome by analyses of serum cortisol, estradiol-17 beta, and estriol levels, and their reponses to ACTH, through the first 3 days of life. The serum cortisol, pregnenolone sulfate and dehydroepiandrosterone sulfate levels of infants with intrauterine growth retardation will be compared to similar measurements in normally grown infants over the first few weeks of life. The objects of these investigations are: the evaluation of the relationship of perinatal adrenal function to the incidence and severity of respiratory distress syndrome; and the elucidation of the dissociation of cortisol metabolite and delta 5-3 beta-hydroxy steroid metabolites excretion by growth retarded newborns. Circulating steroid levels will be quantified by competitive protein binding (cortisol) and radioimmunoassay (estradiol, estriol, pregnenolone, dehydroepiandrosterone) techniques.